Why is the Tartakower variation (4... Nf6 and 5...exf) of the Caro Kann so popular these days?

Until a year ago or so 4. ...Bf5 was considered to be the main line. Nowadays everyone seems to play 1. e4 c6 2.d4 d5 3.Nc3 de 4. Nxe4 Nf6 5.Nxf6 exf. Did some chess streamer or youtuber promote that line? Just being curious.

The tartakower variation is recommended by gotham chess, in general it is easier to play with black an has way less theorie than Bf5

Thanks. This explains the trend. Although I thought his audience are mainly beginners...

There is some detail in the main-line after 5...exf that has been found for black. Don't remember what it is because don't play either side of line, but it is mentioned in thread(s) of opening forum.                           If happened to wander into this line as white, would just assume workable queen-side majority would give me something. Personally think it is dangerous to rely on some novelty, when don't understand position, and don't know what to do if either side deviates from it. 

the Tartakower is a very nice opening.

Around 2017-2019 otb GMs found out about 5... exf6 6. c3 Bd6 7. Bd3 0-0 8. Qc2 Re8+ 9. Ne2 h5!!. It's probably catching up at lower levels by now.

Thanks all for the insightful comments.

I play the Tartakower lines of the Caro-Kann a lot now (including some of the ...h5 ideas), but Levy (GothamChess) has nothing to do with that. I was simply looking for a repertoire change against 1. e4 and the Caro-Kann was one of the few openings I knew practically nothing about. I decided to study this opening and now I play this by repertoire with Black vs 1. e4. 

Fascinatingly enough Leela Chess (Lc0) also utilizes these h5 motifs in the Caro-Kann. I'm not saying all the top GMs are merely expanding on engine preparation, but I'm sure what lines high level engines play is at least some factor which top GMs watch closely. Remember Lc0 was more popular around 2017-2019 than it is now that other engines have contested the top spots.

pfren summarized the situation perfectly, I have nothing more to add except a personal note.

The Caro is my main defense against e4. I tried the Tartakower variation in a few games and wasn't happy with my results. The resulting positions may be objectively fine for black, but they're a different style of position that doesn't suit me as well, so I'm sticking with other lines. There's something to be said for playing for positions that suit your style, even if they aren't "objectively better".

The club players I know who are playing 4...Nf6 5...exf6 don't know anything about ...h7-h5. In fact they don't know anything about the battery Qc2+Bd3, e.g. Kudrin - King, London 1988. https://www.chessgames.com/perl/chessgame?gid=1086790

So perhaps the popularity of 5...exf6 lies with some other reason.

I suspect club players are copying their betters, but they simply haven't learned the theory as far as move 9.

Nothing unusual with that.

its a simple defense to learn. very straightforward and what black should avoid is not complicated. It's also somewhat annoying to play the white side as getting a winning queenside is much easier said than done, if white tries to establish premature he can be down a  pawn or worse.

What do you think about the plan of playing Ne2, Bf4 and Qd2 (instead of the battery with Qc2) trying to exchange as many pieces as possible in order to exploit Black´s pawn structure in the endgame?

i think its popular at the club level because its very easy just to go Bd6-0-0-Re8-Nd7-f80-Qc7